I've just come into possession of an SI-24 and V-Fire. I can get the inputs to show up in REAPER via R-Bus, but playback(and monitoring) gives me no sound.

The Presonus download site mentions a driver and 'MonitorMixer'. I've successfully installed the driver, get 44.1kHz sync(steady blue light on the V-Fire), but no sound is directed back to the SI-24. Is 'MonitorMixer' some sort of virtual patchbay? If so, where is it stashed? I'm missing something simple here...